Resonance frequencies of optical ring resonators are stabilized using integrated heaters, which heat an optical ring resonator to a given temperature. However, various mechanisms cause heat to flow out of the area of the optical ring resonators, including flow of heat into a substrate, which is further facilitated by flow of heat along metal traces to the heaters and any voltage control device used to control modulation at the optical ring resonator. Various techniques have been used to localize heat produced by the heaters at optical ring resonators, for example etching along sides of the devices into the substrate, and under the devices, however such techniques are difficult to implement and require masking of the optical ring resonators, associated devices and metal traces, as well as very careful control of the etching under the optical ring resonators to ensure adequate yield.